In Adobe Media Server 5.0.1, Adobe introduced support for embedding EIA-608/708 closed captioning data inside a video stream for delivery to a client.
To obtain these captions, AMS can extract data from the ATSC Picture User Data, a timed text track, or AMF message sent alongside the video stream.
While this is great in theory, I'm having a difficult time figuring out how one would actually make it work in practice -- namely, what live media encoders will actually preserve ATSC captioning data and pass it along to the server (or pass caption data as an AMF message in the RTMP stream).
What solutions are folks actually using to caption live webcasts?
The Elemental Live and the Inlet Spinnaker/Cisco Media Processor encoders are currently being used in live production to do this. They use OnCuePoint and/or onCaptionInfo to deliver captions in the RTMP streams.